Glad to be of help. I hadn't paid much attention to the missing terminal in FSX until you brought it up. I did find a YouTube video (
) which starts at Terminal 7 and makes the entire loop of terminals at JFK. The gap where T6 once stood is obvious just after the train leaves T7.
Although I knew the history from the 70s era, I had to look up the later information. If you search the internet for
JFK Terminal 6 you'll find articles written by people who were very disappointed at the loss of Terminal 6. I must admit that I remember almost nothing about it, although I did pass through it on several flights to/from the Midwest. On the other hand, I vividly recall TWA's Flight Center in Terminal 5's atrium. I visited it as often as possible, dreaming about the day I would be able to go through the long thin tubes to the boarding gates. I finally had that chance on my honeymoon when we boarded an L-1011 to London. I must say the gate area was a disappointment after seeing the Flight Center. I haven't seen JetBlue's replacement gates, but they have to be an improvement.
BTW I will soon visit T7 next door when we fly to London on British Airways in September. And I get to live another dream when we fly in First Class. I've done Business Class, but this time it'll be the front of the plane for my wife and me.

I'm told First Class on BA is really something, especially at KJFK and EGLL.